[Delphinus]

Hi Carmen,

Replacing the pump probably isn't the answer to the microbubbles. I have forgotten what your sump setup is specifically but looking at that last picture there of it, I'm guessing it's something like a 20g and choosing it was probably based on that it can fit in your stand and so on.

The problem is a 20g is a short sump, and short pumps often don't have enough water contact time to shed bubbles by the time it hits the return pump, and thus you end up with microbubbles.

You might see the occasional sump these days that are split down the middle in the long dimension so that water goes down and back, effectively doubling the linear length of the sump .. although the flip side to these designs is that at half the width, water travels twice as fast.

(I'm not suggestion you revamp your sump like this, just sharing it for informational reasons.)

Anyhow. The problem is water speed through the sump.

As an aside this also means replacing the 90's may have a paradoxical effect as this will speed up the sump return and thus increase the speed through the sump.

But here a few things you can try that don't involve a major re-architecture of the sump:

1) A 100micron filter sock. I have to use these myself because of the cube tank arrangement my sump size is limited and without the sock I get *terrible* microbubbles in the main display.

They don't slow the water speed down any, but what they do do (hee hee .. I just said "do do") is contain the splash effect at the point of sump entry so that less bubbles travel onward in your sump. Plus they help polish your water.

2) Also if you have any baffles that create a level drop, these create a weir effect and this can reintroduce bubbles into the water. So raising the water level in downstream section so that the level drop isn't as pronounced can help.

3) Next, how far is the output of your skimmer from the sump return intake? The bubbles could be coming from your skimmer. What I would do (this is another thing I have to do in my sump) is pipe the skimmer output back to the beginning of the sump. This has dual benefits: 1) bubbles have time to be shed, and 2) it creates a slight recirculation effect with the skimmer (ie., the skimmer reskims some of the water it just skimmed) and thus the water exiting the sump back into the main display is theoretically a tiny bit cleaner.

4) Also, there may be a way to repipe the drain pipework from the tank back to the sump so that water slides in an angle rather than crashing straight down into the sump. The goal is to reduce the splashing effect as much as possible of the water entering the sump.

5) If it really gets unbearable, you could try some kind of Herbie style overflow. Herbie systems are the best for no-microbubbles, any tank I do myself from now on will have Herbie overflows. It is possible to get a Herbie overflow in a tank with a single hole drilled, we just need to get creative on the piping. Sphelps had some diagrams posted up a few months ago if you wanted to go looking at details but if this is something you want to consider at some point, maybe we can talk offline a bit and I'll do what I can to help you out on that one.

Good luck!